The Her2/neu (ErbB2) gene encodes a 185 kDa transmembrane glycoprotein that belongs to the family of epidermal growth factor receptors. It consists of a 620 aa extracellular domain, followed by a 23 aa transmembrane domain and a 490 aa intracellular domain with a tyrosine kinase activity. Akiyama T, et al., Science 1986, 232(4758):1644-1646. These results suggest that ECD/Her2 is a good candidate for a tumor antigen vaccine as it prolongs tumor free survival and overall survival of vaccinated mice.
HER2 antibodies with various properties have been described in Tagliabue et al., Int. J. Cancer 47:933-937 (1991); McKenzie et al., Oncogene 4:543-548 (1989); Maier et al., Cancer Res. 51:5361-5369 (1991); Bacus et al., Molecular Carcinogenesis 3:350-362 (1990); Stancovski et al., PNAS (USA) 88:8691-8695 (1991); Bacus et al., Cancer Research 52:2580-2589 (1992); Xu et al., Int. J. Cancer 53:401-408 (1993); WO94/00136; Kasprzyk et al., Cancer Research 52:2771-2776 (1992); Hancock et al., Cancer Res. 51:4575-4580 (1991); Shawver et al., Cancer Res. 54:1367-1373 (1994); Arteaga et al., Cancer Res. 54:3758-3765 (1994); Harwerth et al., J. Biol. Chem. 267:15160-15167 (1992); U.S. Pat. No. 5,783,186; Kao et al., U.S. Publ. No. 2009/0285837 (2009); Ross et al., The Oncologist 8:307-325 (2003) and Klapper et al., Oncogene 14:2099-2109 (1997), each of which is incorporated herein by reference in its entirety.
The trastuzumab antibody (monoclonal antibody therapy huMAb4D5-8, rhuMAb HER2, trastuzumab, commercially available as Herceptin® (U.S. Pat. No. 5,821,337, herein incorporated by reference in its entirety)) has been the subject of HER-2 research assays. See Sapino, A., et al., Annals of Oncology (2007) 18: 1963-1968; Bussolati, G, et al., British Journal of Cancer (2005) 92, 1261-1267; and Glazyrin A, et al., J Histology & Cytochemistry (2007) 55(1):25-33. Trastuzumab recognizes the extracellular domain of HER-2, but requires modification, for example by biotinylation, to be used in immunocytochemistry and other non-therapy applications. The immunoreactivity of biotinylated trastuzumab, however, is lost after 3 months so that a diagnostic assay with trastuzumab as the primary antibody would never be commercially viable. Moreover, a biotinylated trastuzumab does not recognize a native secretory form of the HER-2 antigen in blood samples in an ELISA assay. Trastuzumab has been shown to be more accurate than the commercially available HER-2 antibodies used for diagnostic uses such as immunohistochemistry, in identifying a subset of HER2-amplified breast cancer patients who are more likely to most benefit from trastuzumab-based treatments. Id.
Accordingly, there is a need for other HER-2 monoclonal antibodies that are more accurate in determining a proper patient population for therapy than the currently commercially available HER-2 antibodies. Moreover, there is a need that such more accurate HER-2 monoclonal antibodies do not require modification, such as with biotinylation, so that they have the confirmed long-term stability necessary for commercial viability in a diagnostic assay. Also HER-2 monoclonal antibodies that recognize a native secretory form of HER-2 protein with high specificity and sensitivity in blood samples for blood and ELISA assays, as well as immunocytochemistry, are needed.